Problems Related to Binomial and Factorial Computations

Dear all,

There are two problems that I have written a code for:

1. Program to determine whether a number is a factorial number or not.

A. I am getting the errors: (a) Linker error - undefined reference to 'WinMain@16' (b) Id return 1 exit status (c) Build Error. My code for this problem is:

Code:

#include<stdio.h>

int main()
{   
    int i,n,prod=1;
    printf("Enter n to be checked");
    scanf("%d",&n);
    if(n==1 || n==2)
    {
            printf("n is a factorial number");
    }
    else if(n>2)
    {   
    for(i=1;i<=n/2;)
    {
     while (prod<=n)
           {
           prod*=i;
           i++;
           }
    }
    }
    if(prod==n)
                {
                printf("factorial");
                }
    else
                printf("not factorial");
    system("pause");
    return(0);
}

2. Program to calculate all the coefficients of x for a given value of n. Here nCr in the rth power of x in the expansion of (x+1)^n is given by

nCr = n! / r! (n-r)!



A. I am getting the errors: (a) Linker error - undefined reference to 'WinMain@16' (b) Id return 1 exit status (c) Build Error. My code for this problem is:

Code:

#include<stdio.h>
int main()
{
    int n,r,i,num,*coefficients,*den1,*den2;
    printf("enter the value of n");
    scanf("the values are %d",&n);
    //for calculating r!
    for(r=0;r<=n;r++)
    {
     if(r==0)
             {
             den1[r]=1;
             }        
     else for(i=1;i<=r;i++)      
             {
             den1[r]*=i;
             }
    }
    //for calculating n-r!         
    for(r=0;r<=n-r;r++)
    {
     if(r==0)
             {
             den2[r]=1;
             } 
     else for(i=0;i<=n-r;i++)
             {   
             den2[r]*=i;
             } 
    }
    //for calculating n!
    for(i=1;i<=n;i++)
                     {
                     num*=i;
                     }
    //for calculating coefficients      
    for(i=0;i<=n;i++)
    {
    coefficients[i]=(num/(den1[i]*den2[i]));
    printf("the %dth coefficient is %d\n",i,coefficients[i]);
    }
system("pause");
return 0;
}

3. Generating the numbers of the Lucas sequence which is a variation of fibonacci sequence. The lucas sequence is:

1 3 4 7 11 18 29 ...

A. This code for this is successfully compiled but on running the program it hangs after entering the value of integer 'n'. My code for this problem is:

Code:

#include<stdio.h>

int main()
{
    int i,n,*a;
    printf("number of terms of the lucas sequence to be calculated");
    scanf("%d",&n);
    for(i=3;i<=n;i++)
    {      
           a[i-1]=3;
           a[i-2]=1;
           a[i]=a[i-1]+a[i-2];
           printf("the lucas sequence to n terms is 1 3 %d",a[i]);
    }           
    system("pause");
    return

Thank you for you help.

Guys the problem to the third question is solved. Thank you for your help .

> A. I am getting the errors: (a) Linker error - undefined reference to 'WinMain@16' (b) Id return 1 exit status (c) Build Error. My code for this problem is:
You're telling the linker that you're creating a GUI program.
But what you actually have is a console program.

Adjust your project settings to create the right kind of project.

First problem also solved! Thank you for your assistance!

I have modified the code for problem 2 (binomial and factorial computations) but my code hangs after I input a number, kindly check the code and let me know:

Code:

#include<stdio.h>
int fact(int a);
int main()
{
    int n,r,i,num,*coefficients,*den1,*den2;
    printf("enter the value of n");
    scanf("the values are %d",&n);
    //for calculating r!
    for(r=0;r<=n;r++)
    {
     if(r==0)
             {
             den1[r]=1;
             }        
     else 
             {
          den1=fact(r);
             }
    }
    //for calculating n-r!         
    for(r=0;r<=n-r;r++)
    {
     if(r==n)
             {
             den2[r]=1;
             } 
     else 
             {   
             den2[r]=fact(n-r);
             } 
    }
    //for calculating n!
    for(i=1;i<=n;i++)
                     {
                     num*=i;
                     }
    //for calculating coefficients      
    for(i=0;i<=n;i++)
    {
    coefficients[i]=(num/(den1[i]*den2[i]));
    printf("the %dth coefficient is %d\n",i,coefficients[i]);
    }
system("pause");
return 0;
}
int fact(int a)
{
         int i,factorial=1;
         for (i=1;i<=a;i++)
         {
                            factorial*=i;
         }
return factorial;
}

Thank you for your reply and help.

First, learn how to indent code.
$ indent -kr -nut -ts2 -i2 bar.c

Code:

#include<stdio.h>
int fact(int a);
int main()
{
  int n, r, i, num, *coefficients, *den1, *den2;
  printf("enter the value of n");
  scanf("the values are %d", &n);
  //for calculating r!
  for (r = 0; r <= n; r++) {
    if (r == 0) {
      den1[r] = 1;
    } else {
      den1 = fact(r);
    }
  }
  //for calculating n-r!
  for (r = 0; r <= n - r; r++) {
    if (r == n) {
      den2[r] = 1;
    } else {
      den2[r] = fact(n - r);
    }
  }
  //for calculating n!
  for (i = 1; i <= n; i++) {
    num *= i;
  }
  //for calculating coefficients
  for (i = 0; i <= n; i++) {
    coefficients[i] = (num / (den1[i] * den2[i]));
    printf("the %dth coefficient is %d\n", i, coefficients[i]);
  }
  system("pause");
  return 0;
}

int fact(int a)
{
  int i, factorial = 1;
  for (i = 1; i <= a; i++) {
    factorial *= i;
  }
  return factorial;
}

Second, get a decent compiler, and use maximum warnings.
$ gcc -W -Wall -Wextra bar.c
bar.c: In function ‘main’:
bar.c:13: warning: assignment makes pointer from integer without a cast
bar.c:33: warning: implicit declaration of function ‘system’
bar.c:19: warning: ‘den2’ may be used uninitialized in this function
bar.c:30: warning: ‘coefficients’ may be used uninitialized in this function


> den1[r] = 1;
Here you dereference a pointer, but you don't initialise it

> den1 = fact(r);
Here you assign your pointer - but not with any useful value.